Recently, human exhaled breath has been widely studied around the world, and these words primarily focus on the relevance of EBCs and VOCs in exhaled breath to human diseases.
To study EBCs and VOCs in exhaled breath, the first step is to collect these two study objects. With regard to a device for collecting EBCs, there are relevant studies around the world, and there already have been some commercialized instruments and devices, which principles rely on that exhaled breath is first passed through a condensation tube, and then the liquid EBCs are collected. Therein, for some devices the cost of detection is increased due to the condensation tube being disposable, and for some other devices the flexibility in application is insufficient due to their large-sized cooler.
Currently, there is no unified standard for the device for collecting VOCs in human exhaled breath, however, there already have been some relevant studies. In a VOCs gas collecting device developed by Michael Phillips, USA, exhaled breath is first blew into one end of a gas container by a disposable mouthpiece, wherein the other end of the gas container is connected to an adsorption tube, the gases in the container are drawn out by the adsorption tube through the other end of the pump, and thus the VOCs in the exhaled breath are captured by the adsorption tube. This device is comparatively automated, however, it takes into account neither the adsorption of the VOCs by the container and other connecting pieces, nor the adsorption temperature of the adsorption tube in every sampling process.
Furthermore, nowadays internationally the existing devices can only collect either EBCs or VOCs, and internationally there is a lack of device which can collect EBCs and VOCs simultaneously, and there is also no report about the studies of integrating two sets of collecting methods into one instrument and performing a subsequent analysis and detection.
To obtain EBCs, exhaled breath is introduced into a cooling system, and water vapor is condensed into liquid by means of a low temperature. EBCs contain water vapor, adenosine, hydrogen peroxide, ions, nitric oxide, prostaglandins, protein and nucleic acid, etc. which are brought out from the lung and the respiratory tract. With the features of simple to collect, non-invasive, acceptable to patients, etc., EBCs may become a new approach for finding the early diagnosis of lung cancer, screening of high-risk groups, etc. However, current common detection means are general immunological methods of which the detection speed is low, the process is complex, and the sensitivity is not high.
A surface acoustic wave (SAW) gas sensor has been widely applied in gas detection. However, since its characteristics are influenced by many environmental factors (such as gas flow, temperature, etc.) and the area of its sensitive region is relatively small so that it is difficult for chemical substances to be fully adsorbed to the sensor surface, its characteristic of high sensitivity cannot be completely achieved. If the working environmental conditions of the SAW gas sensor are not strictly controlled, the goal of rapidly detecting chemical substances with low trace concentrations in human exhaled breath cannot be achieved. A heating rod and a platinum resistor directly inserted in the traditional outlet heating piece of capillary will expand by heat after use, and get stuck in the heating piece, which makes it difficult to replace them.